What is the density of an object that has a mass of 67.0 g and a volume of 14.7 ml?

The density of the object is 4.56. Density is found by dividing mass by volume. I have attached a picture that will help you memorize the formulas for density, mass, and volume.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).